Refrigeration valve and system



Oct. 25, 1966 T. c. KNAEBEL 3,280,582

REFRIGERATION VALVE AND SYSTEM Filed May 25, 1964 2 Sheets-Sheet l FIG. I

FIG. 4

INVENTOR THOMAS C. KNAEBEL BY ATTORNEYS Oct. 25, 1966 c. KNAEBEL 3,280,532

REFRIGERATION VALVE AND SYSTEM Filed May 25, 1964 2 Sheets-Sheet 2 In III-i 7mm 23 I&

iii; l!

Ill, av 33 i FIG. 3

United States Patent 3,280,582 REFRIGERATION VALVE AND SYSTEM Thomas C. Knaebel, Kirkwood, M0., assignor to Standard Machine & Manufacturing Company, St. Louis,

M0., a corporation of Missouri Filed May 25, 1964, Ser. No. 369,788 12 Claims. (Cl. 62-278) This invention relates generally to improvements in a refrigeration valve and system, and more particularly to an improved valve mechanism that can be effectively utilized to reduce the capacity of a compressor or utilized for hot gas defrosting.

An important object is achieved by the connection of the inlet of a by-pass valve to the discharge side of one cylinder of a multiple-cylinder compressor, by the connection of a first valve outlet to the discharge line of another cylinder leading to the condenser, by the connection of a second valve outlet to the suction line leading from the evaporator to the compressor, and by means selectively regulating flow from the valve inlet to either of the outlets in order to provide normal operation of both cylinders in the system or to unload one cylinder to reduce the capacity of the compressor.

Another important object is realized by connecting the second valve outlet to the evaporator inlet on the low pressure side of the expansion valve so that the hot gas discharge from one cylinder is directed selectively to the evaporator coil as long as is required to melt the frost, and then normal operation is restored by selectively directing the flow back to the discharge line through the first valve outlet.

Yet another important objective is afforded by the structural arrangement of the valve inlet and outlets relative to the valve ports regulated by valve elements carried by a stem attached to the piston that is reciprocatively mounted in the valve chamber, which provides an efiicient compact valve unit.

An important object is attained by the unique mounting of the valve stem and of the valve elements on the stem. One end of the valve stem is attached to the piston while the other end is reciprocatively received in a socket formed in a boss projecting into the chamber at one end of the valve body. Another advantage is provided by a passage formed in the boss which communicates the valve chamber with the socket behind the stem end in order to provide an effective and responsive stem action.

Another important objective is achieved by the provision of a tubular sleeve disposed in and secured to the body, the sleeve having opposite ends defining opposed and longitudinally spaced valve ports. An inlet in the body and through the sleeve between the sleeve ends and at one side of the valve ports is placed selectively in communication with the pair of outlets by the action of the valve elements upon reciprocation of the piston and the associated valve stem.

Still another important object is realized by the construction and arrangement of the piston such that a head portion slidingly, yet sealingly, engages the chamber wall beyond the second outlet while in both limits of piston movement, the rear portion of the piston being reduced to provide a space between the rear portion and chamber wall for at least the longitudinal dimension of the second outlet when the second valve element closes the second valve port.

An important object is to provide a valve that is simple and durable in construction, economical to manufacture and assemble, efiicient in operation, and which can be readily installed in a refrigeration system to provide either an unloading of a compressor cylinder to reduce the capacity of the compressor or to provide for hot gas defrosting of the evaporator.

3,28%,5d2 Fatented Get. 25, 1966 The foregoing and numerous other objects and advantages of the invention will more clearly appear from the following detailed description of a preferred embodiment of the valve and of the refrigerant systems in which the valve is utilized, particularly when considered in connection with the accompanying drawings, in which:

FIG. '1 is a diagram of a refrigerant system in which the valve is utilized to reduce selectively the capacity of a compressor having a plurality of cylinders;

FIG. 2 is a cross sectional view of the refrigerant valve;

FIG. 3 is a cross sectional view of the pilot valve with the valve ports moved to the same plane for clarity, and

FIG. 4 is a diagram of a refrigeration system in which the valve is utilized to defrost the evaporator with hot gas.

Referring now by characters of reference to the drawings, and first to FIG. 2, it will be seen that the refrigeration valve includes a substantially cylindrical, tubular body 14 having a chamber 11 therein. One end of the tubular body is closed by a plug 12, the body end and the plug 12 being hermetically sealed as by welding. The opposite end of the tubular body 10 is closed by another plug 13, the end of the body 10 and the plug 13 being hermetically sealed, also as by welding.

Disposed within and secured to the tubular body It is a tubular sleeve 14. The opposite ends 15 and 16 of the tubular sleeve 14 constitute valve seats and define first and second valve ports 17 and 18 respectively. The tubular sleeve 14 is located substantially midway of the tubular body 10 and is provided with a pair of lateral flanges 20 at each end located close to the valve seats 15 and 16 and which sealingly engage the chamber wall of valve body 10.

A fitting 21 is secured to the valve body It the fitting 21 being adapted to secure the valve directly to the discharge side of a compressor cylinder. The fitting 21 includes a bore 22 that communicates with an opening 23 formed in the tubular body .10 and with an aligned opening 24 formed in the sleeve 14. The bore 22 and the openings .23 and 24 constitute the valve inlet communicating directly with the interior of the tubular body 10, i.e., with the chamber 11. The sleeve opening 24 is located between and at one side of the longitudinally spaced valve ports 17 and 18.

A tubular fitting 25 is secured to the tubular body 10 and communicates with the chamber 1'1 through a first outlet 26 formed in body 10 immediately adjacent to the other side of the first valve port 17. Another tubular fitting 27 is secured to the tubular body 10 and provides a second outlet 28 that is located immediately adjacent to the other side of the second valve port 18.

Reciprocatively mounted in the tubular body 10 is a piston 30. The piston 30 includes a head portion 31 that slidably, yet sealingly, engages the wall of chamber 11. An O-ring 32 is carried by the piston head portion 31 and provides the seal between the piston head portion 31 and the tubular body 10. It will be noted that the piston 30 includes a rear portion 33 that is of reduced diameter compared to the head portion 31 so as to provide a space circumferentially between the piston rear portion 33 and the tubular body 10. The piston 30 is provided with a front recess 34 extending centrally through the head portion 31 and partially through the rear portion 33.

An elongate valve stem 35 extends substantially along the longitudinal axis of the tubular body 10 through the tubular sleeve 14 and through the valve ports 17 and 18. The valve stem 35 includes a pair of axially spaced, integral shoulders 36 and 37. The shoulders 36 and 37 serve to position and retain the first and second valve elements 40 and 41 respectively.

Specifically, the first valve element 40 is fitted over the hub 42 of sleeve fitting 43 that is slipped over the stem 35, one side of the first valve element 40 engaging an an- 9 a nular flange 44. For reasons which will later appear, the diameters of the first valve element 40 and its adjacent flange 44 are selected so that the first valve element 40 will engage the valve seat 15 to close the first valve port 17 selectively and yet is spaced from the wall defining the chamber 11 to allow for a free flow of refrigerant through the first valve port 17 into the first outlet 26 when the first valve element 40 is moved to an open position as is illustrated in FIG. 2.. The other side of the first valve element 40 engages a retaining washer 45 disposed between the fitting hub 42 and the stem shoulder 36. A nut 46 is threadedly attached to the stem 35, the first valve element 40 being clamped between the stern shoulder 36 and nut 45.

The second valve element 41 is fitted over and carried by a rearwardly projecting hub 47 on the rear piston portion 33. One side of the second valve element 41 seats against the back of the reduced rear piston portion 30, while the other side engages a washer t) that is located between the piston hub 47 and the stem shoulder 37 The forward end 51 of stem 35 extends through the rear piston portion 33 and into the piston recess 34. A nut 52 is threadedly connected to the stem end 51 and is located within the piston recess 34, the nut 52 clamping the second valve element 41 between the piston portion 33 and the stem shoulder 37.

It will be noted that the rear piston portion 33 and the second valve element 41 are reduced in diameter relative to the piston head portion 31 so as to provide a peripheral space between the tubular body and the piston rear portion 33 andsecond valve element 41 that communicates directly with the second outlet 27. The longitudinal lengthof the reduced rear piston portion 33 and second valve element 41 corresponds substantially to the longitudinal dimension ofthe second outlet 27 so that such space communicates with the second outlet 27 in all positions of the piston 30.

The oppositestem end53 is reciprocatively mounted in a socket 54 formed in a boss 55 formed. integrally with the closure plug 13 and projecting inwardly into the chamber 11. The boss 55 is provided with a small passage 56 that communicates the chamber 11 directly with the socket 54 at the rear of the stem end 53.

The pilot valve associated with this refrigerant valve includes a body 57 provided with a pair of passageways having a common opening 60. One of the passageways has an opening 61 while the other passageway has an opening 62. A valve seat 63 defining a valve port is located in the first passageway between the openings 60 and 61 to regulate flow therethrough. Another valve seat 63 defines a valve port in the other passageway between the openings 60 and 62 to regulate flow therethrough. The opening 60 communicates with the space between the valve ports defined by the valve seat 63 and 64.

A fitting 65 is attached tothe body 57 and places the opening 60 in communication with the valve body space 66 at one side of the piston 30, the tubular fitting 65, being threadedly attached to the closure plug 12. A tube 67 operatively interconnects and places the valve opening 61 in communication with the second outlet 27. Similarly, another tube 68 operatively interconnects and places the valve opening 62 in direct communication with the first outlet 25.

Attached to the top of valve body 57 is a cylindrical tube 70, one end of the tube 70 communicating with the valve opening 61. The other end of the tube 70 is closed by a plug 71. Reciprocatively mounted in the tube 70 is an armature 72. A compression spring 7 3 located between the plug 71 and the armature 72 tends to urge the armature 72 downwardly. A- valve element 74 is carried by the lower end of armature 72, the valve element 74 being adapted to open and close the valve port defined by valve seat 63.

A threaded plug 75 closes the lower end of the valve body 57, the plug 75 being provided with a socket that reciprocatively receives a valve element 76. A rod 77 is attached to and extends between the valve elements 74 and 76 so that such valve elements move as a unit upon reciprocation of the armature 72; The valve element 76 operates to open and close the valve port defined by the valve seat 64. A compression spring 80 is located in the plug socket, one end of the spring 80 engaging the plug while the opposite end engages the valve element 76. The spring 80 tends to urge the valve element 76 upwardly toward a closed position relative to its valve port defined by the valve seat 64.

A solenoid 81 is disposed about the armature tube 70, the armature 81 being located in a casing 82 carried by the upper end of tube 70. The casing 82 is secured to the threaded nipple 83 of end plug 71 by nut 84.

The system in which this refrigerant valve is utilized is shown in FIG. 1. The system includes a compressor 85 having a plurality of or multiple cylinders 86 and 87, each having a discharge side:88. A discharge line 90 interconnects the discharge side 88 of cylinder 86 to a condenser 91'. A liquid line 92 interconnects the condenser 91 to an evaporator 93 through an expansion valve 94. The outlet of. the evaporator 93 is connected back to the compressor 85 by a suction line 95.

The refrigerant valve illustrated in FIGS. 2 and 3 is associated with the other cylinder 87. More particularly, the base fitting 21 issecured directly to the cylinder 87 to place the inlet 22-24 in direct communication with the discharge side 88 of cylinder 87. The first outlet 25 is operatively connected by tubing 96 to the discharge line 90 leading to the condenser 91. Another tubing 97 operatively interconnects the second outlet 27 to the common suction line 95 leading directly to the compressor 85.

In operation, the cylinder 86 of the compressor 85 discharges the refrigerant gas to the condenser 91 through the discharge line 90. The refrigerant moves through the expansion valve 94 to the evaporator 93, and thence back to the compressor 85 through the suction line 95, all in the conventional manner. When the solenoid-operated pilotvalve is not energized, the gas discharged from the cylinder 87 is directed through the first outlet 25 and to the. discharge 90 through the tubing 96, such refrigerant gas joining the discharge from the other cylinders and entering the condenser.

During this normal refrigerant cycle operation, the armature 72 of the pilot valve is in a relatively down position so that the valve element 74 closes the port formed by the valve seat 63 andthereby closes the tube 67. On the other hand, this position of armature 72 causes the valve element 76 to open the port formed by valve seat 64, and hence opens the tube 68 leading to the high pressure outlet 25. Thus it is seen that the valve body chamber 66 at the front side of the piston 30 is subjected to the high pressure existing at the high pressure outlet 25. The suction pressure existing at the second outlet 27 is subjected on the'opposite side of the piston head portion 31 to create sufficient pressure diiferential across the piston to cause the piston 30 to move axially in a direction so that the second valve element 41 is sealed tightly on the valve seat 16 and closes the second valve port 18. Simultaneously,the first valve element 40 moves away from the valve seat 15 and opens the first valve port 17, thereby allowing flow directly from the discharge side of the cylinder 87 to move through the valve inlet 22-24, through the first valve port 17, and thence into the first valve outlet 25.

To reduce the capacity of the compressor 85, the cylinder 87 is unloaded. To unload the cylinder 87, the solenoid-operated pilot valve is energized to halt movement of the discharge gas through the first outlet 25 and tube 96 to the discharge line 90, and directly communicate the discharge side of the cylinder 85 with the second outlet 27 so that the gas is fed directly back into the suction line 95 by tube 97.

When the solenoid 81 is energized, the armature 72 is raised so that tube 68 is closed by the valve element 76 engaging the valve seat 64 and the tube 67 is opened by movement of valve element 74 away from the valve seat 63. Accordingly, the valve body chamber 66 at the front side of the piston 30' is subjected to suction pressure by the open passageway provided through the fitting 65, pilot valve port 60, tube 67 and the second outlet 27. The high pressure gas in chamber 11 is exerted on the opposite side of the piston 34) so that the pressure differential causes the piston 30 to move in a direction so that the first valve element 40 engages the valve seat 15 tightly and effectively closes the first valve port 17, and thereby stops flow of the discharge gas through the first outlet 25. Simultaneously, the movement of the piston 30 causes the second valve element 41 to move away from its valve seat 16, and thereby opens the second valve port 18 in order for the discharge gas to flow directly through the second outlet 27 and thence to the suction line 95 through tube 97.

The discharge pressure of the cylinder 87 now drops to suction pressure and the cylinder 87 is unloaded. In this condition, the power consumed by cylinder 87 consists only of that required to overcome piston friction plus the pressure losses in the piping and valving. High pressure from the other cylinder 86, which is loaded, is present at the first outlet through the tube 96, and hence is subjected to the rear side of the first valve element 4% so that the pressure differential across the first valve element 48" causes the first valve element 48 to maintain its tight seal against the valve seat 15 and keeps the first valve port 17 closed.

Of course, the cylinder 87 can be subsequently loaded and normal refrigeration cycle restored merely by deenergizing the solenoid-operated pilot valve. The position of the component parts of the refrigeration valve and the pressure conditions existing in the valve and system have been described previously with respect to the normal cycle.

FIG. 4 illustrates the utilization of the refrigerant valve in a system so that the hot gas can be used for defrosting purposes. Most of the component parts of the system shown in FIG. 4 are identical to the corresponding parts in FIG. 1, and accordingly are given the same reference characters. The only change of FIG. 4 from FIG. 1 resides in the connection from the second outlet 27.

Briefiy, in FIG. 4, the cylinder 86 of the multiple-cylinder compressor 85 is connected to the condenser 91 by the discharge line 98, the flow from the condenser 91 being directed to the evaporator 93 through the expansion valve 94, and hence directed back to the compressor 85 through the suction line 55. The inlet fitting 21 is attached to the discharge side 88 of the other cylinder 87 in the same manner as shown in PEG. 1. The first outlet 25 is connected to the discharge line 90 by tube 96. However, the second outlet 27 is directed to the evaporator inlet 98 on the low pressure side of the expansion valve 94 by tube 99.

The normal refrigeration cycle is maintained in the manner previously described with respect to the detailed description of the system illustrated in FIG. 1. During this cycle, the solenoid-operated pilot valve is de'energized so that the cylinder 87 is loaded and the gas is discharged from the cylinder 87 through the first valve outlet 25, and hence directed to the discharge line 90 through tube 96 at which point the gas joins the discharge gas of the other cylinder 86 and is fed to the condenser 91.

When the solenoid 81 is de-energized, the armature 72 is maintained in a relatively lower position so that tube 67 is closed and tube 68 is opened in order to subject the valve body chamber 66 at the front side of the piston 30 to the high pressure existing at the first outlet 25. The opposite side of the piston head portion 31 is subjected to the lower pressure conditions existing at the second outlet 27, which is the same as at the evaporator inlet 98. Consequently, the piston 30 is moved rearwardly so that the second valve element 41 sealingly engages the valve seat 16 and closes the second valve port 18, thereby preventing any flow of the hot gas through the second outlet 27. Simultaneously, the first valve element 40 moves away from its valve seat 15 and opens the first valve port 17 so that the gas discharged from the cylinder 87 will be directed to the first outlet 25 and hence to the discharge line through tube 96.

To defrost the evaporator 96, the solenoid 81 is energized in order to raise the armature 72 and thereby close tube 68 and open tube 67 in order to subject the valve body chamber 66 at the front side of piston 30 to the low pressure conditions existing at the second outlet 25, which is the same as that existing at the evaporator inlet 98. The rear side of the piston 30 is subjected to the high pressure in chamber 11 from the hot gas entering the valve inlet 22-24. Consequently, the pressure differential causes the piston 30 to move forwardly so that the first valve element 40 engages its valve seat 15 and closes the first valve port 17, and stops flow of gas through the first outlet 25. Simultaneously, the second valve element 41 moves away from its valve seat 16 and opens the second valve port 18 so that the hot gas discharged from the cylinder 87 is directed through the valve inlet 22-24 and through the second outlet 27, from which it is directed to the evaporator inlet 98 by tube 99.

The rear side of the first valve element 40 is subjected to the high pressure existing in the discharge line 90 provided by the other cylinder 86 by way of the tube 96 and the first outlet 25. The resultant pressure differential across the first valve element 40 maintains the tight seal of the first valve element 48 with its valve seat 15 to keep the first valve port 17 closed.

When the frost is removed from the evaporator 93, the solenoid 81 is die-energized so that the armature 72 is relatively lowered in order to close the tube 67 and open the tube 68. The component parts of the solenoid-operated refrigerant valve will then assume the positions described previously to restore the normal refrigeration cycle.

Although the invention has been described by making detailed reference to a single preferred embodiment of the refrigerant valve and two systems in which the valve is utilized, such detail is to be understood in an instructive, rather than in any restrictive sense, many variants being possible within the scope of the claims hereunto appended.

I claim as my invention:

1. A valve for a refrigeration system comprising:

(a) a body having a chamber,

(b) a piston reciprocatively mounted in the chamber,

(c) a pair of longitudinally spaced valve seats in the chamber at one side of the piston, the seats defining first and second valve ports,

(d) a stem connected to the piston,

(e) an inlet in the body communicating with the chamber between and at one side of the valve ports,

(f) a first outlet in the body communicating with the chamber at the other side of the first valve port,

(g) a first valve element attached to the stem and opening or closing the first valve port to regulate flow between the inlet and first outlet,

(h) a second outlet in the body communicating with the chamber at the other side of the second valve port,

(i) a second valve element attached to the stem and opening or closing the second valve port to regulate flow between the inlet and second outlet,

(j) the first valve element opening the first valve port and the second valve element closing the second valve port in one limit of piston movement, and vice versa in the other limit of piston movement, and

(k) pilot means including a pilot valve-port and a pair of passages communicating with the pilot valve port,

(1) means communicating the pilot valve port with the chamber at one side of the piston,

(m) valve means selectively communicating the pilot valve port with either of the passages,

(11) a tube connecting one of the passages with the first valve outlet, and

(o) a tube connecting the other passage with the second valve outlet, whereby-the piston is subjected to either of the pressures in the first or second valve outlets and thereby moved selectively to the limits.

2. A valve for a refrigeration system comprising:

(a) a body having a chamber,

(b) a piston reciprocatively mounted in the chamber,

() a pair of longitudinally spaced valve seats in the chamber at one side of the piston, the seats defining first and second valve ports,

(d) a stem attached to the piston,

(e) an inlet in the body communicating with the chamber between and at one side of the valve ports,

(f) a first outlet in the body communicating with the chamber at the other side of the first valve port,

(g) a first valve element attached to the stem and located on the outlet side of the first valve port, the

first valve element opening or closing the first valve port to regulate flow between the inlet and first outlet,

(h) a second outlet in the body communicating with the chamber at the other side of the second valve port,

(i) a second valve element attached to the stem and located on the outlet side of the second valve port, the second valve element opening or closing the second valve port to regulate flow between the inlet and second outlet, 7

(j) the first valve element opening the first valve port and the second valve element closing the second valve port in one limit of piston movement, and vice versa in the other limit of piston movement, and

(k) means moving the piston selectivelyto the limits,

(1) the stem is provided with longitudinally spaced enlarged portions providing outwardly and oppositely facing shoulders,

(m) the first valve element being positioned and seated against one of said shoulders,

(11) a nut threadedly engages the stem and holds the first valve element in place,

(0) the second valve element being positioned and seated on the other shoulder,

(p) the piston has a rear portion engaging the second valve element, and

(q) another nut threadedly engages the stem and clamps the rear piston portion and second valve element between the nut and the last said stem shoulder.

3. A valve for a refrigeration system comprising:

(a) a substantially cylindrical tubular body having a chamber,

(b) closure means for the body at each end,

(c) a tubular sleeve disposed in and secured to the body, the sleeve having opposite ends defining first and second valve ports,

(d) an inlet in the body and through the sleeve between and at one side of the valve ports,

(e) a first outlet in the body communicating with the chamber at the other side of the first valve port, :(f) a second outlet in the body communicating with the chamber at the other side of the second valve port,

(g) a pistonreciprocatively mounted in the chamber,

the piston including a head portion slidingly, yet sealingly, engaging the chamber well beyond the second outlet while in both limits of piston movement,

(h) a stem extending through the tubular sleeve and valve ports, the stern t ll ding a pair of longitudi- 8 nally spaced enlarged portions providing oppositely and outwardly facing shoulders, (i) a first valve element carried by the stem and engaging one of the shoulders on the outlet side of the first valve port,

(l) a nut threadedly engaging the stem and retaining (11) the rear piston portion and the second valve ele ment being reduced relative to the head piston portion to provide a space between the chamber wall and the rear piston portion and second valve element at least for the longitudinal dimension of the second outlet when the second valve element closes the second valve port,

(0) one of the closure means including a boss extending into the chamber, the boss being provided with a socket reciprocatively receiving and mounting the other end of the stem, the boss being provided with a passage communicating the chamber with the socket behind the said other stem end,

(p) the first valve element opening the first valve port and the second valve element closing the second valve port in one limit of piston movement, and vice versa in the other limit of piston movement, and

(q) means moving the piston selectively to the limits.

4. A valve as defined in claim 3, in which:

(r) the last said means includes a pilot valve comprising a valve body having a pilot valve port and a pair of passages therethrough communicating with the pilot valve port,

(s) means connecting the pilot valve body to the closure at the opposite end of the cylindrical body and communicating the pilot valve port with the chamber at one side of the piston head portion,

(t) valve means selectively communicating the pilot valve port with either of the passages,

(u) a tube connecting one of the passages with the first valve outlet, and

(v) a tube connecting the other passage with the second valve outlet, whereby one side of the piston head portion is subjected selectively to either of the pressures in the first or second valve outlets and thereby the piston is moved selectively to its limits.

5. In a refrigeration system:

(a) a compressor having multiple cylinders,

(b) a condenser,

(c) a discharge line connectingthe discharge side of one cylinder to the condenser,

(d) an evaporator connected to the condenser and connected to the suction line of the compressor,

(e) a by-pass valve having an inlet and a pair of outlets, the inlet being connected to the discharge side of another cylinder,

(f) one of the outlets connected to the discharge line of Y the said one cylinder, and the other outlet connected to the suction line, and

(g) means selectively regulating flow from the inlet to either of the outlets.

6. A refrigeration system as defined in claim 5, in

which:

(h) the compressor includes a pair of cylinders, each having a common suction line, and

(i) the said other outlet is connected to the common suction line.

7. In a refrigeration system:

(a) a compressor including a pair of cylinders, each having a discharge side and a common suction line,

(b) a condenser,

(c) a discharge line connecting the discharge side of one cylinder to the condenser,

(d) an evaporator connected to the condenser and connected to the common suction line of the compressor,

(e) a by-pass valve including a body having a chamber,

(f) a piston reciprocatively mounted in the chamber,

(g) a pair of longitudinally spaced first and second valve ports at one side of the piston,

(11) a stem connected to the piston,

(i) an inlet in the body communicating with the chamber between the valve ports,

(j) a first outlet in the body communicating with the chamber at the other side of the first valve port,

(k) a first valve element attached to the stem,

(1) a second outlet in the body communicating with the chamber at the other side of the second valve port,

(m) a second valve element attached to the stem,

(11) the first valve element opening the first valve port and the second valve element closing the second valve port in one limit of piston movement, and vice versa in the other limit of piston movement, and

() means for moving the piston selectively to the limits,

(p) the valve inlet being connected to the discharge side of the other cylinder,

(q) the first valve outlet being connected to the discharge line of the said one cylinder, and

(r) the second valve outlet being connected to the common suction line.

8. A refrigeration system as defined in claim 7, in

which:

() the valve body is substantially a tubular cylinder, and includes a closure means at one end of the body having a boss projecting into the chamber, the boss being provided with a socket reciprocatively receiving and mounting one end of the stem.

9. A refrigeration system as defined in claim 7, in

which:

(s) the valve stem includes longitudinally spaced enlarged portions providing outwardly and oppositely faced shoulders,

(t) the first valve element being seated against one of said stem shoulders,

(u) a nut threadedly attached to the stem and clamping the first valve element between the nut and said one stem shoulder,

(v) the second valve element seating between the back side of the piston and the other stern shoulder, and

(w) a nut threadedly attached to the stem connecting the piston to the stem and clamping the second valve element between the back side of the piston and the said other stem shoulder.

10. A refrigeration system as defined in claim 7, in

which:

(5) one end of the valve stem is attached to the piston,

(t) a boss projects into the chamber and is provided with a socket reciprooatively receiving and mounting the other end of the stem,

(u) the stem extending through the valve ports,

(v) the first valve element being located on the outlet side of the first valve port, and

(w) the second valve element being located on the outlet side of the second valve port.

11. A refrigeration system as defined in claim 7, in

which:

(s) a tubular sleeve is disposed in and secured to the valve body, the sleeve having opposite ends that define the first and second valve ports, and

(t) the inlet is formed in the body and through the sleeve between the sleeve ends and at one side of the valve ports.

12. A refrigeration which:

(u) the piston includes a head portion slidingly, yet sealingly, engaging the wall of the chamber beyond the second outlet while in both limits of piston movement, and includes a reduced rear portion providing a space between such rear portion and the chamber wall which communicates with the second outlet while the piston is in both limits.

system as defined in claim 11, in

References Cited by the Examiner UNITED STATES PATENTS 1,575,771 3/1926 King 137-6255 2,589,384 3/1952 Hopkins 62-460 3,099,290 7/1963 Chatham et al 137625.4 3,149,475 9/1964 Gislason 62-197 MYER PERLIN, Primary Examiner. 

5. IN A REFRIGERATION SYSTEM: (A) A COMPRESSOR HAVING MULTIPLE CYLINDERS, (B) A CONDENSER, (C) A DISCHARGE LINE CONNECTING THE DISCHARGE SIDE OF ONE CYLINDER TO THE CONDENSER, (D) AN EVAPORATOR CONNECTED TO THE CONDENSER AND CONNECTED TO THE SUCTION LINE OF THE COMPRESSOR, (E) A BY-PASS VALVE HAVING AN INLET AND A PAIR OF OUTLETS, THE INLET BEING CONNECTED TO THE DISCHARGE SIDE OF ANOTHER CYLINDER, (F) ONE OF THE OUTLETS CONNECTED TO THE DISCHARGE LINE OF THE SAID ONE CYLINDER, AND THE OTHER OUTLET CONNECTED TO THE SUCTION LINE, AND (G) MEANS SELECTIVELY REGULATING FLOW FROM THE INLET TO EITHER OF THE OUTLETS. 